Controlled Neutral Torque Coordination in Hybrid Powertrains
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Solution Overview
Problem
Hybrid powertrain systems lack a conventional mechanical neutral, leading to shutdowns that result in lost vehicle functionality due to torque errors from de-magnetization and part-to-part variations in electric machines, causing unintended vehicle motion.
Innovation Solution
A powertrain system with an internal combustion engine and electro-mechanical transmission that monitors vehicle speed to restrict transitions in low-speed zones, coordinating torque among devices to maintain a net zero output torque condition during controlled neutral operation, preventing unintended motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the hybrid powertrain system shuts down during neutral operation to prevent unintended vehicle motion, then safety is improved, but vehicle functionality is lost
Solution Approach 1:
The patent segments the neutral operation into two distinct modes: conventional shutdown neutral and controlled neutral. In controlled neutral, the system maintains partial operation (engine running, electric machines active) while implementing specific control strategies to prevent unintended motion. This segmentation allows the system to maintain functionality during neutral operation by selectively maintaining certain subsystems while controlling torque output.
Solution Approach 2:
The patent implements dynamic control of torque-generative devices during controlled neutral operation. The control system continuously monitors vehicle speed, torque errors, and operational conditions, dynamically adjusting the torque output of the engine and electric machines to maintain net zero torque while preventing unintended motion. This dynamic approach replaces the static shutdown approach with an adaptive control strategy.
2Adaptability or versatility
If the system operates in controlled neutral without shutdown, then vehicle functionality is maintained, but torque errors from de-magnetization and part-to-part variation may cause unintended motion
Solution Approach 1:
The patent implements a feedback control system that continuously monitors vehicle speed, torque output, and operational conditions during controlled neutral operation. The control system uses this feedback to detect torque errors from de-magnetization and part-to-part variation, and dynamically adjusts the torque-generative devices to compensate for these errors and maintain net zero torque, preventing unintended motion while maintaining functionality.
Solution Approach 2:
The patent applies preliminary anti-action by implementing control strategies that proactively counteract potential torque errors before they cause unintended motion. The system monitors for conditions that may lead to torque imbalances (such as de-magnetization effects) and pre-adjusts the torque output of electric machines and engine to compensate for anticipated errors, preventing unintended vehicle motion before it occurs.
3Reliability
If the engine operating state is restricted in low-speed zones, then unintended motion is prevented, but transition flexibility is reduced
Solution Approach 1:
The patent changes the control parameters dynamically based on vehicle operating conditions. In low-speed zones where unintended motion risk is higher, the system restricts engine operating state transitions and maintains more conservative torque control. At higher speeds where the risk is lower, the system relaxes these restrictions, allowing greater transition flexibility. This parameter change approach allows the system to adapt its control stringency to the actual operating context.
Data Source
AI summary
A powertrain system includes an internal combustion engine, a first electric machine and an electro-mechanical transmission operative to transmit torque to a driveline. A method for controlling the powertrain system in the presence of a controlled neutral operation of the electro-mechanical transmission being selected includes monitoring vehicle speed, and only when the monitored vehicle speed is indicative of a low-speed zone restricting a transition from a current engine operating state.